Instant Unit Conversion
Convert Millimeters to Inches (mm to in)
Exact formula, conversion factors, live calculator, and reference charts for millimeters to inches.
Method reviewed:Exact defined factors — international yard and pound (1959), US customary gallon and cup, SI — the values NIST SP 811 lists · reviewed September 2026
1 millimeter is equal to about 0.03937 inches. To convert millimetres to inches, divide by 25.4 — the exact number of millimetres in an inch.
Live Millimeters to Inches Calculator
in = mm ÷ 25.4Open full length converter →Millimeters to Inches Conversion Table
Quick reference conversion chart from 1 to 100 millimeters.
| Millimeters (mm) | Inches (in) | Mathematical Formula |
|---|---|---|
| 1 mm | 0.0394 in | 1 × 0.0393701 |
| 2 mm | 0.0787 in | 2 × 0.0393701 |
| 5 mm | 0.1969 in | 5 × 0.0393701 |
| 10 mm | 0.3937 in | 10 × 0.0393701 |
| 15 mm | 0.5906 in | 15 × 0.0393701 |
| 20 mm | 0.7874 in | 20 × 0.0393701 |
| 25 mm | 0.9843 in | 25 × 0.0393701 |
| 50 mm | 1.9685 in | 50 × 0.0393701 |
| 75 mm | 2.9528 in | 75 × 0.0393701 |
| 100 mm | 3.937 in | 100 × 0.0393701 |
Frequently Asked Questions
How many mm in an inch?
Exactly 25.4, by definition since 1959. This is one of the few imperial-to-metric conversions that is exact rather than rounded.
What is 10 mm in inches?
10 mm is 0.3937 inches, a shade under two-fifths of an inch.
How do I convert mm to a fractional inch?
Divide by 25.4, then multiply the decimal by 16 for sixteenths. 12 mm is 0.472 in, and 0.472 × 16 is 7.6 — so just over 7/16 inch.